This invention relates generally to the field of vibration reduction and, more particularly, to a reduced-vibration tube array.
Tube arrays are bundles of tubes held in a fixed arrangement to provide a discrete path for fluids. These arrangements are useful in a variety of settings, including heat exchangers, catalytic combustion systems, and other industrial process equipment.
Quite often, tube arrays are incorporated into complex systems, such as industrial gas turbine engines or other multi-components environments. As a result, tube arrays can be subjected to large amounts of vibration during use. If left unchecked, this vibration may damage the array. Weld and braze joint failure at tube/support interfaces and fretting wear at points of inter-tube contact are common examples of vibration-induced damage. The vibration may come from a variety of sources, including fluid motion and vibration induced by remote components or other associated hardware. A variety of approaches have been developed in an attempt to reduce the effects of vibration in tube arrays.
One method of reducing tube array vibration involves bracing the array of tubes with external, lateral support members. These support members are typically placed within the array, between the exteriors of adjacent tubes. During operation, these lateral support members impinge upon the outer surfaces of the tubes and reduce vibration. Although external support members may reduce vibration to some extent, they are not suitable in every situation. External supports may, for example, produce locations of unwanted, concentrated wear which can prematurely age the array and, in some cases, may actually cause tube perforations. External supports may also adversely affect the flow of fluids around tube exteriors; this type of flow interruption can be troublesome or even dangerous. In heat exchanger settings, for example, interrupted fluid flow may lead to inefficient transfer of heat, resulting in reduced operational efficiency. Furthermore, in catalytic combustion systems, overly-reduced flow can be catastrophic, leading to failure of components due to inadequate cooling flow or even xe2x80x9cflashbackxe2x80x9d in cases where flow velocity is too low to prevent flames from travelling upstream, into the tube array.
Internally-disposed damping elements have also been employed to reduce tube array vibration. U.S. Pat. No. 5,158,162, issued to Fink et al. (xe2x80x9cFinkxe2x80x9d) and U.S. Pat. No. 4,590,991, issued to Cooper, et al. (xe2x80x9cCooperxe2x80x9d) are examples of tube arrays that use internally-disposed vibration reducing members. The Fink device discloses a vibration dampener and stiffener apparatus that includes a plurality of flexible, braided cables located within the tubes. As vibration energy is transmitted to the cables, it is transferred into frictional heat energy that radiates from the cables and is dissipated. The Cooper reference discloses a flexible stabilizer for degraded heat exchanger tubing in which an elongated flexible cable or chain is inserted within a tube to be stabilized. With both of these devices, mechanical interaction between the flexible members and tubes reduces vibration within the associated array. Although each approach may reduce vibration in some cases, there still exists the danger of impeded flow, which, as described above, may lead to inefficiencies and can be dangerous.
Although various attempts to reduce vibration within tube arrays have been developed, there are shortcomings which still remain. Accordingly, a need exists in the art for a reduced-vibration tube array assembly that is customizable and which provides desired flow characteristics without producing reductions in effectiveness or reliability. The assembly should dampen vibrations within the array tubes without unduly restricting fluid flow through the array. The assembly should be customizable, allowing strategic, localized variations to account for various aspects of the array tubes. The assembly should also impart desired fluid flow within the array and should transfer vibration energy at multiple transfer locations to provide a distributed transfer of load.
The instant invention is a reduced-vibration tube array assembly. The assembly includes a plurality of tubes held in a fixed relative relationship and elongated, contoured damping members located therein. The damping members are sized and shaped to permit desired fluid flow rates through the associated tubes. Reduced flow rates may be accommodated by highly-contoured (e.g., tightly spiraled) damping members which provide strategically-selected resistance to flow. Enhanced flow rates may be accommodated by more xe2x80x9cflow-transparentxe2x80x9d damping members (e.g., members with fewer spirals, having less cross-sectional area, made with perforations, or even made of porous media.) Each damping member is characterized by at least one interface region that has bracing points which contact the inner surfaces of an associated tube during use. During operation of the array, unwanted vibration energy in the tubes is advantageously transferred to the damping members at the bracing points and is dissipated. The bracing points provide multiple locations of contact between the tubes and bracing members, thereby producing a distributed transfer of load. The damping members may be individually customized and may include localized variations to accommodate selected regions of significance within the array. For example, tubes at the periphery of the array may be adjoined on one side by a flat wall rather than by identical tubes. More (or less) dampening may be desired near such a discontinuity. Damping members of different mass or contour may be used advantageously with such periphery tubes. As another example, an unsupported section of a tube with otherwise-discrete locations of support may require increased dampening. A fin-like damping member cold be non-spiraled at the locations of support and tightly spiraled in unsupported regions to yield efficient dampening. In this manner, the interface between the bracing members and the tubes may be customized to provide interaction which will dissipate energy effectively, without damaging the tubes or interfering with the functionality of the array.
Accordingly, it is an object of the present invention to provide a reduced-vibration tube array assembly that is customizable, allowing strategic, localized variations to account for various aspects of the array tubes.
It is another object of the present invention to provide a reduced-vibration tube array assembly that produces desired flow characteristics without producing reductions in effectiveness or reliability.
It is a further object of the present invention to provide a reduced-vibration tube array assembly that dampens vibrations within the array tubes without unduly restricting fluid flow through the array.
It is an additional object of the present invention to provide a reduced-vibration tube array assembly that imparts desired fluid flow within the array.
It is also an object of the present invention to provide a reduced-vibration tube array assembly that transfers vibration energy at multiple transfer locations to provide a distributed transfer of load.
It is additionally an object of the present invention to provide a reduced-vibration tube array assembly that produces supplemental securement of the tubes to the tubesheet.
It is yet another object of the present invention to provide a reduced-vibration tube array assembly that produces enhanced mixing of internal and external tube fluids downstream of their exits.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.